The goals of this study are to use BDNF-LacZ transgenic "knock-in" mice to determine the role of BDNF in adult mouse taste cells. The first aim will determine which taste cell types express BDNF in the adult mouse. Specifically, whether BDNF is present in newly divided taste cells, immature taste cells, or phenotypically mature taste cells. If BDNF is present in mature taste cells, I am interested in determining which immunohistochemical and morphological classes of taste cells BDNF is present in. I will use double-label immunohistochemistry to achieve this aim. To birthdate cells I will inject mice with 5'-Bromo-2' deoxyuridine which incorporates into the DNA of dividing cells. I am also interested in determining what effect(s) loss of taste bud innervation will have on the expression of BDNF and what effect(s) subsequent regeneration and innervation of taste buds will have on the expression of BDNF. To achieve this aim I will surgically crush the gustatory nerves in BDNF-LacZ mice and let the mice live for successively longer days post nerve crush to look at the effect(s) nerve degeneration and regeneration has on BDNF expression in taste buds. For my final aim, 1 am interested in determining what effect(s) adult loss of BDNF expression in taste buds has on taste buds, gustatory nerve fibers and gustatory ganglion cells. Since I am interested in looking at the effect loss of BDNF expression has on the adult taste system and I do not want to disrupt the initial development of taste buds, I will use a tissue-specific conditional knockout mouse and knockout BDNF expression only in the tongues of adult mice. I can also denervate the taste buds in the tissue-specific conditional BDNF knockout mice to see whether nerve fibers will regenerate and reinnervate taste buds that no longer express BDNF. This aim will determine the role(s) of BDNF in adult mouse taste cells, without affecting the initial development of taste buds.